/*
 * Spreed WebRTC.
 * Copyright (C) 2013-2015 struktur AG
 *
 * This file is part of Spreed WebRTC.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package main

import (
	"crypto/rand"
	"math/big"
	pseudoRand "math/rand"
	"time"
)

const (
	dict = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
)

// NewRandomInt returns a random integer in range [0, max[
// Tries to use crypto/rand and falls back to math/rand
func NewRandomInt(max int) int {

	rand, err := rand.Int(rand.Reader, big.NewInt(int64(max)))
	if err != nil {
		// Fallback to pseudo-random
		return pseudoRand.Intn(max)
	}
	return int(rand.Int64())

}

func NewRandomString(length int) string {

	buf := make([]byte, length)
	for i := 0; i < length; i++ {
		buf[i] = dict[NewRandomInt(len(dict))]
	}
	return string(buf)

}

func init() {
	// Make sure to seed default random generator.
	pseudoRand.Seed(time.Now().UTC().UnixNano())
}